Method for gravel or frac packing in a wellbore and for monitoring the packing process

Abstract

A method for gravel packing or frac packing in a borehole includes running a workstring to a target location, running an optic fiber to the location with the workstring and monitoring the target location with the optic fiber. A method for monitoring at least one parameter at a plurality of discrete locations at a gravel packing or frac packing location in a borehole including running a workstring to the gravel packing or frac packing location running an optic fiber to the gravel packing or frac packing location along with the workstring and monitoring the gravel packing or frac packing location at a plurality of discrete points along the gravel packing or frac packing location.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to provisional application 60/712,529 filed Aug. 30, 2005, the entire contents of which are incorporated herein by reference.

BACKGROUND

The hydrocarbon exploration and recovery industry has learned in recent years about the capabilities of optic fibers acting as sensing/monitoring implements in the downhole environment. Typically such fiber is disposed within a control line to protect the fiber itself from the mechanical and chemical effects of the environment yet allow for sensory reception of conditions all along the fiber. Control line containing fiber is permanently installed in the wellbore at a multitude of time frames during well construction but never is it removed from the wellbore unless it has malfunctioned. This is in part because fiber is relatively fragile and handling fiber can lead to its degradation. The art is well aware of this and therefore takes pains to limit the amount of handling to which fiber is subjected. Therefore the benefits of fiber optic sensing/monitoring in the wellbore have been utilized ubiquitously but only for permanently installed assemblies.

Gravel packing and frac packing operations, common to wellbore operations are built with temporary workstrings that are run in the hole to deliver a slurry to an annular section of the borehole. Progress, as is well known to those of skill in the art, is monitored using annulus pressure measured at the surface. The measured pressure is corrected by subtracting the hydrostatic pressure of the fluid column in the borehole. The annulus pressure is thus measured indirectly. Since this practice has been in use for a long time, well operators are familiar with the nuances thereof and can use the process effectively. Unfortunately, such prior art methods are limited in their resolution of useful information and inability for direct measurement.

SUMMARY

A method for gravel packing or frac packing in a borehole includes running a workstring to a target location, running an optic fiber to the location with the workstring and monitoring the target location with the optic fiber.

A method for monitoring at least one parameter at a plurality of discrete locations at a gravel packing or frac packing location in a borehole including running a workstring to the frac packing location running an optic fiber to the gravel packing or frac packing location along with the workstring and monitoring the gravel packing or frac packing location at a plurality of discrete points along the gravel packing or frac packing location.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings wherein like elements are numbered alike in the several Figures:

FIG. 1 is a schematic view of a section of a borehole where a frac packing operation is taking place illustrating a circulating flow pattern known to the art and a runnable optic fiber at a workstring; and

FIG. 2 is a schematic view of the same portion of the well without the workstring after gravel packing or frac packing and completing of the well, illustrating absence of the fiber optic.

DETAILED DESCRIPTION

The art to which the current disclosure relates is benefited by additional information about the downhole environment. Well operators are all to painfully aware that most of what is done downhole is done by expectation and then judged inferentially by empirical evidence of something related to the target inquiry. Such is the case for gravel packing or frac packing operations.

For frame of reference, FIG. 1 illustrates a pack zone 10 in a wellbore with a screen system 12 and packer 14. A workstring 16 is also depicted with a crossover assembly 18. A ball 20 dropped from surface at an appropriate time diverts flow of fluid slurry as is known. Flow of slurry is indicated by arrows throughout the drawing and will be recognized by those of skill in the art.

What is distinct about the workstring 16/packing zone 10 is that an optic fiber conduit 22 is run in the hole with the workstring and is not a permanent installation in the downhole environment. In fact, conduit 22 is configured to be run in the hole with the workstring from its own reel and then reeled back out of the hole as the workstring is tripped out of the well.

Prior art packing operations measure pressure inside screens 12 and transmit that pressure reading to surface. The pressure “seen” by a sensor at the locations indicated is the applied fluid pressure from the slurry and the hydrostatic pressure from the column of fluid to surface. In order to determine pack pressure therefore, one must subtract the hydrostatic pressure to deduce rather than directly measure annulus pressure. While this works as noted above, it provides the well operator only a vague idea of the overall picture downhole. By contrast, the method disclosed herein allows the operator to get a picture of the whole of the formation face in the packing area. This is because of the provision of the optic fiber conduit 22 comprising a fiber within a control line. The optic fiber control line arrangement allows for a plurality of discrete parameter measurements along its length such as pressure measurements. By enabling more discretely located pressure measurements, particularly in a gravel packing or frac packing operation, precise areas and ratios of leak off of fluid into the formation can be identified and therefore mapped. Areas of annular bridging during the gravel packing or frac packing process can also be identified in real time. By measuring multiple discrete locations across the face of the formation at the frac packing location over time, for example, a true picture of the fracing activity and the packing of the fractures can be generated. The availability of information of this type allows for real time determination of the effect of certain parameters of slurry injection and applied pressure at the surface. This gives the operator the insight to adjust pumping parameters to optimize the gravel packing or frac packing operation, thereby improving the specific operation and improving ultimate production in the wellbore.

In order to promote the advantages stated, the method herein teaches one to provide a reel of fiber optic conduit 30 (one or more optic fibers inside a control line) at a surface location or other remote location and feed that conduit into the wellbore while tripping the workstring 16 into the hole. The fiber optic conduit is secured to the outside of the workstring 16 above the gravel pack assembly, and washpipe 17 within the screen in pack zone 10 by conventional clamps (not shown) as the workstring 16 and washpipe 17 is run in the hole. The crossover assembly 18 is a feed-through type used to pass the fiber optic conduit through the gravel pack between the upper drill pipe workstring 16 and to a downhole end of the washpipe 17 within the screens. This feed-through is done similarly to passing control lines through production and gravel pack packers. Surface-based equipment is connected to the optical fiber (laser, controls and interrogation computer) to conduct the optical data gathering operation. The output is displayed on a graphical monitor in real time. The optic fiber conduit 22 is then used to monitor selected parameters above noted.

Upon completion of the frac packing operation, and while the workstring is tripped out of the hole, the conduit 22 is re-reeled for storage and use another day. After removing the workstring 16 and conduit 22, a production tubing string 32 (see FIG. 2) is stabbed in and production can ensue. It will be appreciated in FIG. 2 that there is no unnecessary obstruction in the well and no openings through the packer as would be the case with permanently installed optic fiber conduits.

It will be understood that an optic fiber within a control line is not itself new and is known to one of ordinary skill in the art. Therefore, specific discussion of the optic fiber/control line itself is not required.

While preferred embodiments have been shown and described, modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.

Claims

1. A method for gravel packing or frac packing in a borehole comprising:

running a workstring to a target location;

running an optic fiber to the location with the workstring; and

monitoring the target location with the optic fiber.

2. A method for gravel packing or frac packing in a borehole as claimed in claim 1 further including:

packing the target location.

3. A method for gravel packing or frac packing in a borehole as claimed in claim 1 wherein the monitoring includes querying the target location at a plurality of discrete selective points therealong.

4. A method for gravel packing or frac packing in a borehole as claimed in claim 1 wherein the method further includes mapping the target location using selective monitoring of a plurality of points therealong.

5. A method for gravel packing or frac packing in a borehole as claimed in claim 1 wherein the method further includes removing the optic fiber from the borehole.

6. A method for gravel packing or frac packing in a borehole as claimed in claim 1 wherein the removing of the optic fiber occurs with the removal of the workstring.

7. A method for gravel packing or frac packing in a borehole as claimed in claim 1 wherein the optic fiber is run inside a control line.

8. A method for gravel packing or frac packing in a borehole as claimed in claim 1 wherein the monitoring includes measuring pressure at plurality of discrete selected points within the target location.

9. A method for gravel packing or frac packing in a borehole as claimed in claim 1 wherein the monitoring includes measuring temperature at plurality of discrete selected points within the target location.

10. A method for monitoring at least one parameter at a plurality of discrete locations at a gravel packing or frac packing location in a borehole comprising:

running a workstring to the gravel packing or frac packing location;

running an optic fiber to the gravel packing or frac packing location along with the workstring; and

monitoring the gravel packing or frac packing location at a plurality of discrete points along the gravel packing or frac packing location.

11. A method for monitoring at least one parameter at a plurality of discrete locations at a gravel packing or frac packing location in a borehole comprising:

disposing an optic fiber at a workstring in the downhole environment while the workstring is in the downhole environment;

measuring at least one parameter of the downhole environment at a plurality of discrete locations; and

removing the optic fiber from the downhole environment while the workstring is removed from the downhole environment.

12. A method for monitoring at least one parameter at a plurality of discrete locations at a gravel packing or frac packing location in a borehole as claimed in claim 11 wherein the optic fiber is disposed within a control line.

13. A workstring comprising provision for association therewith of an optic fiber such workstring and optic fiber being runnable into and out of a borehole over short duration.